A sensitive microplate hemagglutination-inhibition technique has been used to ascertain the distributions of secreted blood group substances (BGS) in a population of 176 semen specimens and to characterize the stability of these substances in dried semen stains. The BGS concentrations in semen were found to vary throughout a wide range of titer. Despite this latitude of variation, the titers for the component BGS within the blood groups could be described by a lognormal distribution function. Studies of a number of sequential semen specimens obtained from the same donors revealed that the intraindividual variation in BGS titers was much more limited than the interindividual BGS titers. Attempts to correlate variations in titers between A and H in Group A semen or B and H in Group B semen indicated that the levels of these component substances vary independently.

Studies of the stability of BGS in Groups A and O semen suggested that these substances were stable when the semen stains were stored at −20°C, 4°C, or at ambient laboratory temperature in a dry state. In contrast, stains stored at 37°C under hunmid conditions suffered a dramatic loss in BGS titer, with the half-life of the BGS being on the order of 30 days.